footer {
    position: fixed;
    left:0;
    bottom: 0;
    width: 100%;
    height: 50px;
    line-height: 50px;
    text-align: center;
    background:white;
}

footer ul {
    list-style: none;
    display: flex;
}

footer ul li {
    flex:1;
}

.active{
    color:red;
}